refactor(git): make the git module self-contained under git.util

lua/git/log.lua

@@ -1,7 +1,6 @@
 local git = require("git")
-local log = require("log")
 local repo = require("git.repo")
-local util = require("util")
+local util = require("git.util")
 
 local M = {}
 
@@ -21,7 +20,7 @@ function M.show(opts)
 
     local _, worktree = repo.resolve_cwd()
     if not worktree then
-        log.warning("not in a git repository")
+        util.warning("not in a git repository")
         return
     end
 
@@ -38,7 +37,7 @@ function M.show(opts)
         table.insert(cmd, "--max-count=" .. max_count)
     end
 
-    local stdout = util.system_sync(cmd, { cwd = worktree })
+    local stdout = util.exec(cmd, { cwd = worktree })
     if not stdout then
         return
     end